The mechanism of luteinization in the rhesus monkey and pig will be investigated using cultures and suspensions of granulosa cells. Once a mechanism is obtained using the in vitro approach it will be confirmed and extended in vivo in the rhesus monkey. A thorough examination of the mechanism involved in production of granulosa cell gonadotropin receptors during follicular maturation will be made. As an extension of this it is hoped to find out more about the nature of LH and FSH receptors using I125-hCG as a marker for the LH receptor and I125-FSH as a marker for FSH receptors. Cyclic 3', 5' - AMP levels which are sensitive to LH will also be used as a measure of gonadotropin action. Since there appears to be a luteinization and oocyte maturation inhibitor within the follicle, follicular control of luteinization and oocyte maturation will be examined in cultures of monkey follicles. The role of gonadotropins as well as other hormones such as insulin, thyroxin and cortisol in granulosa cell luteinization will be examined in cultures of monkey and porcine granulosa cells grown in chemically defined media. In order to test the physiological significance of the in vitro studies, substances thought to be involved in luteinization will be injected into follicles of the rhesus monkey and their effects on luteinization observed. Control of luteinization in normal and pathological conditions can better be understood once the mechanism of luteinization is known.